AS I stood among the 5,000 people in Burlington, Vermont's waterfront park while Bernie Sanders launched his Democratic presidential primary bid late last month, it was odd to hear the repeated claim that Sanders was responsible for rescuing this very parkland from rapacious developers while he was mayor of Burlington in the 1980s.

This story is emblematic of Sanders' political history. While he says many good things that socialists support and that attract support from workers, students and the left, his actual political practice is at odds with his image. Setting aside his self-identification as a "socialist," even his claim to be "independent" is dubious once you know about Sanders' accommodations with business and the wealthy and his ongoing collaboration with the Democratic Party.

[T]he question for us isn't mostly about the "purity" of Sanders' political positions. The crux of our objection is Sanders' decision to run for the Democratic Party presidential nomination, and to promise in advance that he will endorse the mainstream Democrat who will all but certainly defeat him.

Such critiques of Sanders focus rightly on the role he will play--indeed, which he has promised, in his own words, to play--within the Democratic Party in the coming year: as the liberal "sheep dog...charged with herding activists and voters back into the Democratic fold," as Bruce Dixon of Black Agenda Report put it.

But at the same time, anyone who disagrees and thinks that radicals should get involved in the Sanders campaign--or even merely welcome it as an opportunity to build the left--should consider just how "impure" Sanders' record is. Here's what we in Vermont have learned about Bernie Sanders over the years.

- - - - - - - - - - - - - - - -Political Independence

Bernie Sanders' political career began as part of the left-wing and antiwar Liberty Union party in 1972, when he ran for U.S. Senate against Vermont's now-ranking Sen. Patrick Leahy.

But after the end of the Vietnam War and the retreat of the antiwar and other social movements of the 1960s, Sanders followed a rightward trajectory into a close relationship with the Democratic Party. He has supported one Democratic presidential candidate after another, starting with Jimmy Carter in 1976 and 1980. In 1984, he actively campaigned for Carter's former vice president Walter Mondale.

Early on in his political career, Sanders challenged both parties of the billionaires. But the pull of the Democratic Party was strong. By the time of his 1990 election to Congress, Sanders was backed by Vermont's Democratic Party establishment. He had left any challenge to this capitalist party behind.

As former Vermont Gov. Howard Dean, also an aspirant for the Democratic presidential nomination in 2004, said 10 years ago on the NBC's Meet the Press, "He is basically a liberal Democrat, and he is a Democrat at that--he runs as an Independent because he doesn't like the structure and money that gets involved...The bottom line is that Bernie Sanders votes with the Democrats 98 percent of the time."

- - - - - - - - - - - - - - - -Labor and Workers' Rights

Based on his unapologetic pro-union politics, Sanders receives considerable labor support in Vermont and nationally. Leading labor officials regularly share the platform with Sanders, who calls for union rights, fair contracts and pro-working class economic policies.

But what does the Sanders campaign offer a new generation of labor activists who want to rebuild a class struggle labor movement? His verbal support for workers is useful, but of secondary importance in rebuilding union power. Whether workers can turn the tide is dependent on their ability to organize on-the-job actions, including shutting down production through strikes, pickets and solidarity.

Toward the end of the strike, Sanders reportedly made calls to management in support of the drivers' demands. But this was only after union members, working together with labor and community activists, organized a strong strike that won widespread public support, including bus riders inconvenienced by the walkout. The political leaders who supported the strike only did so because of the unity of the drivers and solidarity from other working people.

But whatever credit Sanders deserves for his stance in the bus drivers' strike, it is overshadowed by his allegiance to and collusion with the Vermont Democratic Party as it has carried out attacks on public-sector workers.

Sanders is known nationally for opposing austerity policies and decrying declining wages and lack of good union jobs for U.S. workers. His proposals for a national jobs program and expansion of the social safety net are a stark contrast to mainstream Democrats.

But it must be said as well that Sanders' populism is also based on protectionist policies and economic nationalism that are the opposite of internationalism.

While the left should oppose guest-worker programs designed for U.S. corporations to hire low-wage labor without full legal rights and the capacity to unionize, it's a different matter to argue, on the basis of nationalism, to bar immigrant labor because this harms American workers. International investment knows no bounds, and if the labor movement is to fight effectively, it has to struggle on the basis of cross-border class solidarity, not support for policies that pit workers of different national origins against each other.

Sanders can't look to the Democrats for support for his protectionism. It was the Democratic Party under Bill Clinton that passed North American Free Trade Agreement, established the World Trade Organization and cut big trade deals with China. President Barack Obama is currently pushing the Trans-Pacific Partnership (TPP) economic agreement with empty promises about how it will benefit U.S. working people.

Ominously, Sanders' economic nationalism has led him to look for allies among Republican right-wingers like Lou Dobbs and Patrick Buchanan, who see China as a rival to U.S. power and are looking for political justification for a new Cold War.

In denouncing Permanent Normalized Trade Relations (PNTR) with China, Sanders wrote, "As the greatest democracy on Earth, we must ask why American companies are turning communist China into the new superpower of the 21st century? While Microsoft is 'saving a dollar,' it is helping undermine our economic and military security by gutting our manufacturing and technological infrastructure, and moving it lock, stock, and barrel to one of our major international rivals."

Sanders defends his alliances with protectionist Republicans. He told the Nation magazine, "In the sense that we are trying to develop left-right coalitions, we also trying to redefine American politics." Thus, he appeared on a China-bashing panel organized by the Teamsters' Jimmy Hoffa along with Patrick Buchanan in 2000 during a union-sponsored demonstration against PNTR for China.

Like Sanders, the labor movement regularly blames free trade agreements for causing the bulk of job losses in the U.S. According to studies, however, trade policies account for only a portion of manufacturing job losses. More significant has been Corporate America's drive to increase productivity--making fewer workers work harder and produce more. Sanders' nationalist lens and support for protectionism diverts attention from the overwhelming cause of manufacturing job loses--the profits-first priorities of American big business.

Sanders' populism puts him more in alliance with a wing of U.S. capital that seeks advantages through trade and investment restrictions, not the international working class. This is not a socialist position, nor one that can help strengthen the labor movement by working to organize cross-border solidarity.

- - - - - - - - - - - - - - - -Racism and Police Violence

One of the naked contradictions of Sanders' political development lies in these two facts: In the 1960s, he was a civil rights activist who campaigned against police brutality, among other abuses. But in 1981, when he ran for mayor of Burlington, he won the support of the city's police union.

Sanders' political career has continued to lean in the direction of law and order. Once elected to Congress, he voted for the Violent Crime Control and Enforcement Act in 1994--one of the infamous Clinton crime bills that billions of dollars to states to beef up local police forces and prisons, and that expanded the federal death penalty to include 60 new offenses.

An article at Salon.com blamed Sanders' "socialist analysis" for emphasizing class issues over fighting racism. While Sanders' politics, indeed, have little to offer the Black Live Matter movement, his lackluster-at-best attitude to fighting racism is not the product of a "socialist analysis" by any stretch. Socialists support struggles against all oppressions in all their dimensions, social, economic and political. This is a central tenet of Marxism.

In the U.S., fighting racism and its enforcement though the New Jim Crow and police terror must be central to any movement for progressive change. Racism is the main ideological tool used by the U.S. ruling class to justify the neoliberal assault on social welfare programs, austerity and privatization in public education, and public-sector union-busting.

To socialists, the anti-racist struggle--including the fight to defund and disarm police--is crucial to building working-class unity, not only so we stop bigotry and hate, but to fight back against the billionaires and build for a socialist future.

As Sanders makes his way out of Vermont, Iowa, and New Hampshire and onto the national stage, he may follow Hillary Clinton's lead in acknowledging the problem of police violence and mass incarceration, but his politics around race and police violence, while acceptable to the Democratic Party establishment, is a dead end for the Black Lives Matter movement.

- - - - - - - - - - - - - - - -War and U.S. Empire

Some of the most poignant criticisms of Bernie Sanders have come from opponents of Israeli apartheid. Sanders continues his support for Israel even after the 2013 massacre in Gaza and despite the significant headway made by the international boycott, sanctions and divestment (BDS) movement in exposing real nature of the Israeli state.

The question Sanders should have to answer is this: Why does solidarity with oppressed workers end at the U.S. border and not extend to, among many others, Palestinians living under the yoke of Israel's apartheid state?

Israel has more and more justified the ethnic cleansing and oppression of Palestinians as part of the global fight against terrorism--both benefitting from and contributing to the U.S. "war on terror" against Arabs and Muslims.

In the same way, Sanders has embraced the whole narrative that justifies the U.S. wars and occupations since 9/11 as a fight against Muslim extremists who represent a threat to the U.S. He began in the aftermath of the September 11 attacks, voting to support George Bush's war on Afghanistan with the Authorization for the Use of Military Force.

At the kickoff rally for his Democratic Party presidential campaign, Sanders got the most applause when he repeated that he voted against the invasion of Iraq in 2003. This was also one of his most deceptive sound bites.

In 1990, when Sanders was running to be Vermont's sole member of the U.S. House of Representatives, he addressed a large crowd of antiwar protesters on the eve of the first Gulf War launched by George Bush Sr. While the Bush administration was pursuing its pro-war propaganda offensive to demonize Saddam Hussein, Washington's one-time ally, as a threat to invade the whole region, Sanders told a startled crowd that he deferred to the judgment of the Pentagon on this question.

Sanders' record of support for U.S. wars and empire is broadly consistent. His House and Senate votes supported the NATO war in ex-Yugoslavia in 1999, the invasion of Afghanistan in 2001 and war budgets to finance the occupation of Iraq. There have been some votes here and there to reign in the stupidity of U.S. or Israeli overreach--something that Sanders has in common with the likes of Barack Obama and Hillary Clinton. But Sanders generally embraces a world order in which the U.S. military reigns supreme.

The U.S. government's $1 trillion annual war budgets undermine the possibility of initiating or expanding any of the social and jobs programs that Sanders regularly talks about in his speeches. Simply put, there will be no substantial progress on issues like social welfare, education, jobs and more without a fundamental challenge to the U.S. empire--something Sanders has resisted throughout his national political career.

The working class town of Winooski, that sits at the end of the runway, voted by referendum to join a lawsuit against the basing. Despite this and other examples of opposition, Sanders lined up with commercial real estate interests, the military-industrial complex and, of course, Vermont's leading Democrats to back the basing, protecting the state's lucrative pipeline to the Pentagon.

Sanders defenders falsely claim that senator backed the F-35 to protect Air National Guard jobs, but these were never on the line. In reality, Vermont's celebrated "independent" won't buck the state's ruling class when it comes to cutting off a source Pentagon funds, and he won't challenge the U.S. war machine that these bombers will be a part of.

- - - - - - - - - - - - - - - -Climate Change and the Environment

Since the 1990s, Sanders has consistently raised the threat of climate change due to greenhouse gas emissions. In speeches, he talks about the need to transition away from fossil-fuel production to renewable energy sources. Environmental activists look to Sanders as a champion--thus, 350.org's Bill McKibben gave a rousing speech at the Burlington kickoff rally.

But Sanders' championing of the environment seems to only apply on one side of the partisan divide. He relentlessly targets the billionaire Koch brothers, the Republicans and climate-change deniers--but barely mentions the equally culpable role of the Democratic Party.

As exposed by Wikileaks, one of Barack Obama's first significant actions on the issue of climate change as president was to work behind the scenes to undermine the Copenhagen climate talks in 2009--and this was quickly followed by his running political cover for BP after the Deepwater Horizon disaster in the Gulf of Mexico.

What is the benefit of having a president who, in contrast to his Republican predecessors, stresses the danger of climate change--but then works to obstruct international negotiations on limiting greenhouse gas emissions, while boasting about the record increase in U.S. oil and natural gas productionopening up drilling in the Arctic?

As much as any other crisis, climate change is the inevitable outcome of capitalism's drive for growth and profits. It would have been valuable for a socialist politician to say that--instead of focusing all his criticisms against Republicans and their billionaire supporters, while remaining silent about the Democrats.

This is another issue where Sanders says a lot of the right things, but his actions--and his silences--speak louder than his words.

Under the weight of the new left's retreat and the nearly four-decades-old ruling-class offensive, many of those inspired to struggle for social change have been pulled by the idea of "political realism" into the Democratic Party and the liberal infrastructure tied to it. The key idea is that progressive change will only come in cooperation with the business and political establishment that rules the U.S.

Sanders' political views are more in keeping with this tame liberalism. If his self-identification with "socialism" is valid at all, it is with what revolutionaries have called "socialism from above," disconnected from the class struggle that Karl Marx, Frederick Engels and Sanders' supposed hero Eugene Debs believed was indispensible for a fundamental challenge to the capitalist system and winning a socialist world.

Sanders' history shows what happens when you accept the restrictions and limitations that come with "political realism." The lesson of history is that radicals who attempt to change the system from the inside end up changed themselves. In Sanders' case, this has meant accommodating to U.S. empire and military budgets, silence at best on police violence and the Jim Crow system of mass incarceration, and collaboration with business interests and at least one of their wholly owned political parties.

What the struggles for social change need today is not a liberal outsider running a long-shot campaign in the Democratic presidential primaries, but a clear break from the Democrats on the basis of a left-wing political alternative. There is no shortcut through the party of the billionaires. In this election, like past ones, the place for radicals is building any independent challenges to the two parties of the status quo.